The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
A synchronizer, or dog clutch, is employed in automatic and manual transmissions to synchronize the speed of two components prior to engagement of those two components. Generally speaking, a synchronizer includes a sleeve and a blocker ring. The sleeve has a set of teeth and is rotationally fixed to a first component and is longitudinally translatable along an axis of rotation to engage a set of teeth located on a second component. Longitudinal movement of the sleeve toward the direction of the second component initially causes a frusto-conical surface of the blocker ring to engage a matching frusto-conical surface on the second component prior to engagement of the teeth. Engagement of these two surfaces is a clutching action which causes the second component to be speed synchronized with the blocker ring and sleeve and thus the first component. During this speed synchronization, the blocker ring acts as a torque transmitting member which prevents the alignment of the sleeve teeth with grooves or notches in the blocker ring. Once synchronization occurs, friction on the blocker ring is relieved and the blocker ring is free to rotate slightly relative to the sleeve. The sleeve teeth then engage blocker ring teeth thus rotating the blocker ring and bringing into alignment the grooves or notches with the sleeve teeth. As the sleeve continues to move longitudinally, the sleeve teeth pass through the grooves or notches and engage and index with the teeth on the second component. At full engagement or full stop of the sleeve, the first component, the synchronizer, and the second component all rotate together.
However, as the sleeve pushes past the blocker ring after synchronization but before gear indexing, drag on the blocker ring can increase the rotational torque acting on the blocker ring. Thus, as the sleeve teeth engage the blocker ring teeth to move past the blocker ring, any increased rotational torque acting on the blocker ring increases the axial force, or blocker release load, required to push the sleeve past the blocker ring.
Typically, the teeth on the sleeve, blocker ring, and on the second component include oblique surfaces which cooperate during engagement to prevent inadvertent disengagement and to reduce indexing loads and blocker release loads. Typically the teeth on the sleeve and the blocker ring have been shaped to have 45 degree angles. While these designs are robust to wear they result in relatively high blocker release loads. One solution is to simply reduce the surface angles relative to a longitudinal axis of the teeth, thus reducing the blocking release loads. However, this results in narrow teeth having relatively small cross-sections that are not robust to wear. Therefore, there is a need in the art to provide a synchronizer that is robust to wear, reduces blocker release loads, improves cold shift quality, overcomes sticky synchronizers, reduces transmission drag losses, and harmonizes upshift and downshifts.